Nicholas Cullinan, who is to be director of the National Portrait Gallery in London. Photograph: Metropolitan Museum of Art/PA

Cullinan said: “It is with great pleasure that I return to the National Portrait Gallery, an institution that I have grown up with and where I first worked 14 years ago.

“At a time when identity, shared culture and civic values are increasingly relevant to us all, the National Portrait Gallery is uniquely placed to generate a discussion by reflecting on our common artistic, cultural and social history – in short, what binds us together.

“It will be an honour to lead the gallery at a particularly exciting time in its development, to build upon its remarkable success and accomplishments and to work with its world-class team in shaping the future direction.”

Cullinan, 37, was born in Connecticut but grew up in Yorkshire. Before being lured to the Met, he was at Tate Modern for six years, becoming curator of international modern art and working on exhibitions including Cy Twombly: Cycles and Seasons (2008) and Edvard Munch: The Modern Eye (2012).

Educated at the Courtauld Institute of Art, he worked at the NPG as a visitor services assistant while he was a visiting teacher for his MA course. His duties included directing visitors around the gallery, giving talks about portraits and working on the information desk.

Sir William Proby, the chair of trustees at the NPG, said of Cullinan: “He is an outstanding curator and art historian, and has wide-ranging international experience. We believe his flair and enthusiasm will allow us to build on the excellent work Sandy Nairne has done over the past 12 years.”

Cullinan will take up the post in the spring, but will not be the gallery’s youngest director; that honour belongs to Roy Strong, who was 32 when appointed in 1967.

At about the same time a new boss is expected at the NPG’s neighbour, with trustees at the National Gallery soon to announce a successor for its departing director, Nicholas Penny. Among the candidates for that post are former National Gallery curators Gabriele Finaldi, who is currently the deputy director of the Prado in Madrid and narrowly missed out on the job last time; Luke Syson, head of European sculpture and decorative arts at the Met who was responsible for the National Gallery’s Leonardo show in 2011; and Axel Ruger, director of the Van Gogh museum in Amsterdam.

Two other leaders of Dutch museums are also in the frame – Taco Dibbits, the Rijksmuseum’s director of collections, and Emilie Gordenker, a former curator at the National Gallery of Scotland and director of the Mauritshuis in The Hague.